1. Field of the Invention
The present invention relates to an outboard engine provided with an internal combustion engine having a throttle valve device capable of being easily operated from outside the outboard engine and of being neatly arranged inside an engine cover covering the internal combustion engine.
2. Description of the Related Art
A prior art outboard engine provided with an internal combustion engine and a throttle valve device combined with the internal combustion engine, and disclosed in JP 8-91297 A uses a push-pull cable, namely, a Bowden cable, for transmitting a throttle operating force to a driven part of the throttle valve device.
In the outboard engine disclosed in JP 8-91297 A, the inner cable of the Bowden cable is connected to a control lever disposed in a front part of the outboard engine, another cable is extended between a drive pulley combined with the control lever, and a driven pulley combined with the throttle valve device disposed in a rear part of the outboard engine. The inner cable of the Bowden cable is moved relative to the outer cable of the Bowden cable to turn the driven pulley in a desired direction for opening or closing the throttle valve device by the drive pulley.
Since the drive and the driven pulley respectively having certain diameters are used for transmitting the sliding motion of the inner cable of the Bowden cable to the valve shaft of the throttle valve device, a comparatively large space available for placing the drive and the driven pulley must be formed around the throttle valve device and hence the size of the engine cover needs to be increased.
In most conventional outboard engines, a vertical internal combustion engine is disposed with its crankshaft extended in a vertical position in a front part of the outboard engines, an intake duct connected to the intake port of the internal combustion engine is extended on the right or the left side of the internal combustion engine, and the intake duct and a throttle valve device connected to the intake duct are placed inside an engine cover covering the internal combustion engine. In the following description, terms qualifying directions and sides, such as right, left, front, rear, longitudinal and lateral, are used to qualify directions and sides with respect to the advancing direction of a ship provided with the outboard engine.
In most cases, a valve shaft holding the throttle valve of the throttle valve device is vertically extended, a throttle lever for turning the throttle valve has a base part connected to the upper or the lower end of the valve shaft and a free end connected directly or through links to an operating member, such as a push-pull wire.
In the outboard engine of this type, the valve shaft is supported in an upper bearing part and a lower bearing part, and water collects in the lower bearing part and, in some cases, the water collected in the lower bearing part hinders the light operation of the throttle valve device.
An outboard engine disclosed in JP 11-34985 A is provided with a throttle valve device having a throttle valve supported on a valve shaft, and placed in an intake duct with the valve shaft extended in a horizontal position.
In the outboard engine disclosed in JP 11-34985 A, a throttle lever connected to the valve shaft supporting the throttle valve, and a link connecting the throttle lever to a push-pull wire are arranged outside the intake duct, and a throttle position sensor for measuring the angular position of the throttle valve is connected to an outer end, lying outside the intake duct, of a shaft supporting a turning lever connecting the throttle lever and the push-pull wire. When the throttle lever, the link and the throttle position sensor are arranged outside the intake duct, the engine cover covering the internal engine of the outboard engine needs to be formed having a bulge and it is difficult to form the outboard engine in a compact construction.
The present invention has been made in view of the foregoing problems and it is therefore an object of the present invention to provide an outboard engine provided with a throttle valve device requiring a small space for installation, and a small engine cover that does not need to be formed having a bulge.